In traditional PDRE (pulse detonation rocket engines), mechanical valves are used for periodic supply control and a purge process is widely used to form a buffer zone to prevent fresh fuel-oxidizer mixture from pre-ignition. However, both of them increase hardware complexity and limit increase of operating frequency. To eliminate mechanical valves and the purge process, a valveless mode without the purge process has been proposed. Multi-cycle detonations are able to create periodic pressure oscillations inside a detonation tube, which are capable to interrupt fuel and oxidizer supply. In the present study, liquid gasoline was used because vaporization of the liquid fuel would cool hot combustion products, which acted as a buffer zone. Therefore, a liquid-fueled and valveless PDRE without the purge process became possible. When oxygen-enriched air with 25% similar to 45% oxygen by volume was employed, a maximum operating frequency of 110 Hz was achieved. It was observed that supply pressures of fuel and oxidizer were of great importance for such an operating mode. Exhaust plumes at different operating frequencies were also investigated. The results indicated that it was feasible for the valveless PDRE to run steadily without the purge process when liquid gasoline was utilized. (C) 2014 Elsevier Ltd. All rights reserved.